Tunnel kiln



Nov. 20, 1923A G. H. BENJAMIN TUNNEL KILN heet l Sheets-S C Nif/,7,

1,474,616 G. H. BENJAMIN TUNNEL Km:

Filed Feb, 8. 1922 5 Sheets-Sheet' 2 Q w O QQOOGQGGOGOQoOOGwGGOOGoOK Nov. 20, 1923 3 Sheets-Shut 5 G. H. BENJAMIN TUNNEL KILN Filed Feb. 8,

.INVENTOR N`,

Nov. 2o, 1923.

Patented Nov. 20, -1923.

UNITED STATES A GEORGE HILARD BENJAMIN, OF NEW YORK, N.l Y.

TUNNEL KILN.

Application led February 8, 1922.A Serial No. 534,839,l

To all 'whom t concer/n.:

Be it known that I, GEORGE HILLARD BEN- JAMIN, a citizen of the United States of America, residing at New York, county of New York, State of New York, have invented a certain new and useful Improvement in Tunnel Kilns,.of which the followz which the hea-ting, as well as the regulation expensive.

ing is a specification.

My invention relates to improvements in tunnel kilns; of which the following is a specification.

Tunnel kilns have heretofore been heated directly, by the combustion of coal, or indirectly by the .combustion of gas and air,

or oil and air. Both methods have'v been open to objections; the principal one of which is, however, that it is found dtiicult to control the heat, i. e., to meet the requirements for variation of .heat along the length of the kiln. When the heat cannot be reg-v ulated, the result, for instance in treating pottery, .is the production of a large number of seconds. This is most objectionable and T0 overcome the objection of the lack of vheat regulation, I have' devised the construction described in this specification, in

of the heat, is effected through the ap*L lication of electrically developed heat in one portion of the length of the kiln, or alternatively, by the combined effect `of heat developed through the combustion of gas and air in one portion of the length of the kiln, and heat developedby electricity in another portion of the kiln.

In the accompanying drawings, I nave shown my invention applied to kilns of the open as also of the muffle type.v I havev also shown various features of construction which are applicable not only 'to kilns containing my present improvements in heating, but to kilns heated by the older methods as above set forth; all of which improvements will be specifically pointed out in the specification.

The accompanying drawings, which are largely diagrammatic, will serve to illustrate my invention, in which, p

Fig. 1 us a longitudinal vertical section, with certain of the parts in elevation.

Fig. 2 is a horizontal section taken along 'the 1in@ n n of Fig. 1.

Fig. 7 is. al longitudinal vertical sectioncorresponding to Fig. 1, which shows a construction difering from Fig. 1, in that the means for distributing the heat is locatedbelow theklin structure, whereas in Fig. l,

it is above the kiln structure.

Fig. 8 is a vertical transverse section along the line of VIII- VIII of Fig. 7.

Fig. 9 is a diagram of the circuit connections.

In the drawings, 5

construction. The kiln structure in Figs 1 and.y 7 is divided into three zones in the direction of the length of the kiln, A, B and C; A being the preliminary heating zone, B the zone of high temperature,and C the cooling zone.

In Fig. 4, the two heating' zones A.' and B are shown, and itis assumed that a cooling zone C, not shown inthis figure, will be added to the right of the zone B in the actual kiln.A

The interior of the kiln forms the main or treating chamber 6, and is provided with tracks 7, over which are adapted tobemoved,

lcars 8, which carry the goods to be treated.l

rep-resent's vthe kiln structure which may be of any suitable low entrance of the cars into, and exit from,

the kiln. Situated on each side of .the-kiln in the zone B, Figs. 1 and 7, and zones A and B, Fig.'4, are pairs of heating chambers 10. These chambers are structurally independent of the walls of thejkiln and of each other.

In Figs. 1, 2 and 3 the heating chambers are formed with a single continuous wall 11, with openings 12 at the top; whereas, in Figs. 4, 5 and 46 the heating chambers are formed with double walls, 1,1 and 13, with openings 12 at the top; openings 14 at the bottom, and openings 15 at the to of the wall 13; the arrangement of 4, 5 an 6 being such as to leave a space 16, between the walls 11 and 13.

Situated in the bottom'of the heating chambers are two blocks 17 and 18, such as a refractory carbon. Located between these blocks is a third block 19, of high resistance material. The blocks 17 and 18 are given such shape as to support the block 19 above the bottom of the heating chambers. Arranged over and covering the blocks 17 and 18 and 19 is a body of high resistance material 20, preferably lump carbon. Located in the openings 12 of the chamber are carbon electrodes 21 connected to any suitable source of electricity through conductors 22. In Figs. 3,l 5 and 6 the electrodes are surrounded with sleeves 23.

In Figs. 1, 2 and 3, the gases developed by the combustion in the heating chambers can flow through the openings 12 into the cavity of the heating chamber 6.

In the construction shown in Figs. 4, 5 and 6, by means of the sleeves, the gases are discharged out of the kiln. By reason of this condition, the construction shown in Figs. 1, 2 and 3 may be termed an open kiln. whereas that shown in Figs. 4. 5 and'l. a Inutile kiln.

The electrodes. as will be seen by the dia-` electrodes, but by putting into operation one or both pairs of electrodes. The temperature can be determined by thermometer 26, introduced into the top of the kiln over the heating chambers. 1

In. the operation of the kiln, therefractory resistance material 20 is gradually destroyed and it is necessary to remove and replace it. Provision is made for removing refractory resistance material through the doors 27, at one end of each of the heating chambers.

Referring again to Fig. 1, means is disclosed for conveying the surplus heat from the cooling zone into the preliminary heating zone A, which means consists of a picking-up chamber 28. Located over the top of the kiln, is a flue 29 and pump 30, and a flue 31 from pump 30 leading into the forward end of thepreliminary chamber A.

In Fig. 7, the picking-up chamber consists of a series of openings 32 in the bottom of the side walls of the kiln, which lead through iue 33 to pump 34, thence through flue 35 to a series of openings 36 in the bottom of the side walls of the preliminary heating chamber.

In this figure, a second series of openings 37 in the bottom of the side walls of the preliminary heating chamber A, communicate through flue 38 with the pump 39, adapted to discharge through the flue 40 to the atmosphere.

vIn the upper portion of the side walls in the construction is an opening 41 connected with the Hue 42 through which the heat in the cooling chamber C, may be withdrawn and a similar opening 43 is shown in the top of the side wall of the preliminary chamber. In Fig. 4, the preliminary heating chamber is provided with heating chambers, tired by the combustion of gas and air introduced by the burners 44. The products of combustion are carried away by stacks 45.

The operation of my improved kiln is as follows The door 9 at the left hand end of the kiln is raised, and a car carrying the material to be treated is introduced into the kiln. The car remains in the chamber A for a sufficient time to thoroughly heat the material carried on the car,at'ter which the door 9 is again opened and a second car introduced. As successive cars are introduced, the first car passes into thc zone B, where it is subjected to the highest tempera'tureand maintained at such temperature during the time the cal' is in zone B and is gradually cooled as the ear approaches the right hand end of the kiln.

The heat carried by the material passes upward into, the picking-up space 28, and the picking-up flue 29, and is delivered into the zone thus conserving the heat. By the pump 39, F ig. 7, the heat in zone A can be regulated. Any surplus heat in A or C may be withdrawn through flues 41 and 43.

So far as relates to the construction shown in Fig. 4, it is practically the same as that shown in the other figures, with the exception that means are provided for heating the zone A by heat derived by the combustion of gas and air. This seems desirable in treating materials which require a high temperature at the time they are introduced into the kiln. and a higher temperature during the time the goods are passing through zone B.

It will be understood that in the construction shown in Fig. 4, the features of the construction shown in Fig. 1 and Fig. 7 for controlling heat from zone C and delivering it into zone A, can also be employed.

In this specification, I have described the heating means of zone B as effected by the passing of electric current between the electrodes, with an interposed resistance in the nature of a refractory material. Manifestly, other means of generating electric heat may be employed. ,I am aware that it has heretofore been proposed to heat kilns by heat developed by electricity, and such I do not broadly claim; my invention being limited to the application of electric heat when.

used in connection with heating chambers, disposed as, and having the general construct-ion illustrated in the drawings.

By reason of my improved construction, the heat can not only be regulated within practical limits, but by reason ofthe air circulation, surrounding the heating chambers, effective distribution of the heat is 0btained, and all danger of over-heating of materials under treatment, at the sides of the cars, and where exposed to the highly heated heating chambers, is avoided.

It will be understood that owing tothe construct-ion of the heating chambers, and their relation to the walls of the kiln, there is a constant circulation of heated air from the bottom of theA kiln, upward, around the heating chambers, to the top of the kiln, and then downward, through the material on the carriages; this circulation being continuous and automatic.

Having thus described my invention, I claim 1. A tunnel oven comprising a main chamber through which .goods to be heated can be caused to travel; a heating chamber o n each side of the main chamber, structurall' independent of the side walls and root' of t 1e chamber; and means in each chamber for converting and transmitting electric current into heat.

` 2. A tunnel oven comprising a main chamber -a heating chamber located on each side of the main chamber, but structurally independent therefrom; a body of high electrical resistance in each heating chamber; and spaced electrodes in each of said chambers in contact with the material of high electrical resistance.

3. A tunnel oven comprising a main chamber; a heating chamber located on each side of the main chamber, but structurally independent therefrom; a body of material of high electrical resistance, situated in each chamber; spaced pairs of electrodes in each chamber in contact with the material of high electrical resistance; a sleeve surrounding each electrode external to the heating chamber, communicating at one end with-the heating chambers, andv at the other end with the exterior ofthe kiln, whereby the gaseous bodies generated in the heating chambers will be conducted from the heating chambers to the exterior ofthe kiln.

4. A tunnel oven comprising a main chamber; a heating chamber located on each Side of the mam chamber; a cleaning door at one end of each of the heating chambers;

together With means for generating electric heat in the interior of the heating chambers.

5. A tunnel oven comprising a mam chamber; and divided longitudinally into three zones; a preliminary heating zone, a high temperature zone, and a cooling zone, a heating chamber located in the zone of high temperature; together with means for setting free heat due to the passage of electric current from the resistance medium within the heating chamber, whereby the heat in the body of the kiln will be that radiated from the heating chamber.

6. A tunnel oven eoniprising a main chamber; and divided longitudinally into three zones; a preliminary heating zone, a high temperature zone, and a cooling zone; a heating chamber located in the zone of high temperature; together with means for setting free heat within the chamber by the, passage of an electric current `through a high resistance medium, and means for conveying the excess 0f heat from the cooling` zone. and delivering it into the preliminary heating zone.

7. AItunnel oven comprising a main chamber; a heating chamber; said heating chamber formed Withcontinuous walls perforated at the top at two points; said chamber located at a distance from the bottom. side and top Walls of the kiln, whereby air ma be circulated around the chamber; a body of material of high electrical resistance situated in the heating chamber; and a pair of electrodes, having their lower terminal ends in the cham-ber, and in contact with the material of high electrical resistance; and their upper terminals ends connected in multiple toa source of electric energy.

8. The herein described method of heating the treating chamber of a continuous kiln; which consists in developing electrical hea t within a chamber situated within the treating chamber, but structurally independent therefrom.

In testimony whereof, I aflix my signal ure, in the presence of two witnesses.l

GEORGE HILLARD BEiTJAMIN.

IVitnesses;

HENRY PRICE BALL, FLORENCE A. CHAPPLE. 

